GNU – Open Source

Free software means that the software’s users have freedom. (The issue is not about price.) We developed the GNU operating system so that users can have freedom in their computing.

Specifically, free software means users have the four essential freedoms: (0) to run the program, (1) to study and change the program in source code form, (2) to redistribute exact copies, and (3) to distribute modified versions.

Software differs from material objects—such as chairs, sandwiches, and gasoline—in that it can be copied and changed much more easily. These facilities are why software is useful; we believe a program’s users should be free to take advantage of them, not solely its developer.

Open Sources: Voices from the Open Source Revolution

This is an freely available O’Reilly book on the Tanenbaum vs. Torvalds debates, defiantly a great read.